ECS Instances and Amazon ECS Service Endpoint

Answer: A and C.

The container agent runs on each infrastructure resource within an Amazon ECS cluster.

It sends information about the resource's current running tasks and resource utilization to Amazon ECS, and starts and stops tasks whenever it receives a request from Amazon ECS.

Refer page 328 on the below link:

https://docs.aws.amazon.com/AmazonECS/latest/developerguide/ecs-dg.pdf

Option A is correct.ECS supports interface VPC endpoints.

https://docs.aws.amazon.com/AmazonECS/latest/developerguide/vpc-endpoints.html

https://aws.amazon.com/blogs/aws/aws-privatelink-update-vpc-endpoints-for-your-own-applications-services/

Option B is not correct.

Any network communication in/out of VPC must follow the rules defined on route tables, Network ACLs and Security Groups.

Any external communication (internet facing or AWS service endpoints) must either go through Internet Gateway, NAT Gateway or VPC Endpoints (if applicable).

Option C is correct because this container instance can communicate with the Amazon ECS service endpoint with its public IP address.

For more information on traffic between VPC and outside networks, refer to documentation here.

https://aws.amazon.com/premiumsupport/knowledge-center/connect-vpc/

Option D is not a valid statement.

Refer to the above documentation.

Sure, I'll provide a detailed explanation for each option.

Option A: Create an Interface VPC Endpoint for ECS service and attach to VPC subnet's route table in which ECS instances are running.

This option is correct. When you run Amazon ECS tasks or services in your VPC, you can create an interface VPC endpoint for the Amazon ECS service. An interface endpoint is an elastic network interface with a private IP address that serves as an entry point for traffic destined to a supported service. By creating an interface VPC endpoint, you can connect to Amazon ECS without requiring an internet gateway, NAT device, VPN connection, or AWS Direct Connect connection. To enable Amazon ECS to communicate with your interface endpoint, you need to attach the endpoint to the route table of the subnet where your Amazon ECS instances are running.

Option B: ECS instances are launched with ECS-optimized AMI which contains an inbuilt mechanism to communicate with ECS service endpoints through AWS network.

This option is also correct. When you launch Amazon ECS instances, you can choose an Amazon Machine Image (AMI) that's optimized for Amazon ECS. This AMI includes the Amazon ECS container agent, which is a component of the Amazon ECS container agent and is required on every Amazon ECS container instance. The agent communicates with the Amazon ECS service to register the instance, retrieve task definitions, and send container logs. The agent also sends heartbeats to the service to indicate that the instance is active and available to run tasks.

Option C: Container instances have public IP addresses.

This option is not correct. Amazon ECS container instances don't have public IP addresses by default. If you need to access a container instance from outside of the VPC, you can use a NAT gateway, a VPN connection, or an AWS Direct Connect connection to provide the instance with internet connectivity.

Option D: AWS service endpoints are accessible internally across VPCs. You need to enable IAM role access on the service which needs to be accessed.

This option is not correct. AWS service endpoints are accessible within a VPC or VPC peering connection. To access an AWS service endpoint from a different VPC, you need to create a VPC peering connection between the VPCs. IAM roles control access to AWS resources, but they don't affect the ability to access service endpoints across VPCs.

To summarize, options A and B are correct statements concerning ECS instances when accessing the Amazon ECS service endpoint. Option C is incorrect, and option D is also incorrect as it doesn't specifically address the correct way to access the Amazon ECS service endpoint.